DESCRIPTION (adapted from the abstract): Although several of the evolutionary conserved players in the metaphase to anaphase transition have been identified, key questions remain concerning the regulation of anaphase promoting complex (APC), the function of individual APC subunits, and the possibility that APC and its checkpoint regulators also function in meiosis. The long-term goal of this project is to define, in molecular detail, the combination of shared and unique cellular processes which drive and/or regulate the metaphase to anaphase transition during germline mitosis, oocyte meiosis, and spermatocyte meiosis in the nematode, C. elegans. C. elegans is particularly well suited for these studies since mutant defects in mitosis and meiosis can be studied simultaneously within a single animal. The specific aims of this proposal are: 1) to complete the basic molecular and genetic characterization of emb-27, a gene which is required both for germ cells to proliferate, and for oocytes and spermatocytes to complete their meiotic divisions, 2) to initiate studies of other genes required for the metaphase to anaphase transition (MAT) through the analysis of both temperature sensitive mutants as well as embryos in which the expression of selected APC genes been disrupted by RNA mediated interference, and 3) to order the phenotypic defects of emb-27 and other MAT mutants relative to known substages of the metaphase to anaphase transition. These studies are expected to reveal both novel and conserved players in this important cellular process. The conserved proteins will be directly relevant to our understanding of how defects in chromosome segregation lead to cell death, birth defects and/or tumor progression, whereas the non-conserved proteins may identify new targets for treatment of nematode parasitic infections.